Signal selector device



May 6, 1958 H. H. ABELEW SIGNAL SELECTOR DEVICE 5 Sheets-Sheet 1 Filed March 18, 1954 IIGAIF May 6, 1958 H. H. ABl-:Lew

SIGNAL SELECTOR DEVICE 5 Sheets-Sheet 2 L N. N.

Filed March 18, v1954 ATTORNEY May 6, 1958 H. H. ABELEW SIGNAL SELECTOR DEVICE Filed March 18, 1954 5 Sheets-Sheet Z5 INVENTOR bf ,451225 W ATTORNEY May 6, 1958 H. H. ABELEW SIGNAL SELECTOR DEVICE 5 Sheets-Sheet 4 Filed March 18, 1954 VQ. Si

l .E l J lNvi-:N-roR A( H ABELEW ATTORNEY United States Patent O SIGNAL SELECTOR DEVICE Harry Hugo Abelew, Brooklyn, N. Y., assignor to Mackay Radio and Telegraph Company, New York, N. Y., a company of Delaware Application March 1S, 1954, Serial N o. 416,981

7 Claims. (Cl. 340-164) This invention relates generally to improvements in signal selecting apparatus adapted to discriminate between a certain type of signals and all other signals not of that type.

This is a continuation-in-part of applicants co-pending application, Serial No. 254,121, tiled October 31, 1951, entitled Signal Selector Device.

A primary purpose of the invention resides in the provision of an improved selector apparatus particularly adapted for use as a selector of automatic alarm signals currently comprising, for example, a series of dashes, four seconds in duration and separated by one second intervals, Such a signal has been internationally adopted for actuation of automatic alarm systems for marine use to eliminate the necessity of an operator remaining on continuous duty for detection of radioed distress signals. Selectors currently employed in connection with systems of this type are electro-mechanical in nature and are adapted to operate through a range for acceptance of dashes 3.5 to 6 seconds long, separated by time intervals of fromQl to 1.5 seconds. Upon reception of, for eX- ample,` three or four consecutive accepted dashes, the selector actuates a warning circuit, and any combination of static or other electrical interference which does not in eiect constitute a signal falling within the limits of tolerances prescribed for the auto alarm signal, does not operate to actuate the warning circuit. One type of such an electromechanical system is disclosed in U. S. Patent 2,235,804 to Macalpine.

Certain inherent disadvantages reside in the electromechanical type of automatic alarm selectors, due, for example, to mechanical inertia and to the time lags associated with electro-magnetic coils employed therein, such time lags being commonly of the `order of several milliseconds. Specications for auto-alarm systems are drafted by international conventions and substantial reductions of allowed tolerances are currently under consideration. Proposed specifications, now agreed upon, impose great diiiculties in respect to the design of electro-mechanical equipment for operation within dened tolerances.

Therefore, an important object of the present invention is to provide an automatic alarm selector device wherein electron devices are employed with a periodic circuit of negligible Q for suitable reduction of the response time of the selector.

A still further object is to provide an improved circuit of this type utilizing standard stock components and which does not require components selected for a specific electrical magnitude.

Another object is to provide an improved apparatus, the operation of which may be readily checked by visual inspection of indicating devices, and which maybe easily maintained in proper operating condition.

A still further object resides in the simplification of adjustment controls in discriminator type alarm signal Selector apparatus, a single control being employed for variation in the timing of the dashes as well as spaces of signals to be accepted, eliminating the need of independent adjustments in timing, thereby obviating one source of timing errors.

Another object of the invention is to provide an improved automatic alarm selector apparatus suitable for employment of counter tubes of the cold cathode type to effect simplification of the circuitry and reduction in the number of required components.

Another object of the invention is to improve and simplify automatic alarm selector apparatus for one or more of the purposes above mentioned. Other objects will readily become apparent to persons skilled in the art upon examination of the drawings, the description, and claims appended thereto.

In the drawings, in which like parts are identit-led by the same reference numerals,

Fig. 1 illustrates in block diagram, the general arrangement of components of a device employing the principles of the present invention.

Fig. 2 illustrates in block diagram certain components of an electronic timing relay of a type particularly adapted for use in the device of Fig. l.

Fig. 3 shows in chart form, the sequence of operation of the various gates shown in Fig. 1.

Figs. 4A, 4B and 4C are a schematic diagram of an embodiment of my invention.

Fig. 5 shows how Figs. 4A, 4B and 4C should be placed side by side.

Fig. 6A is a chart of the operation of the counting stages in the dash timing relay which is used in the device of Fig. l.

Fig. 6B is a chart of the operation of the counting stages in the space timing relay which is used in the device of Fig. l.

Use is made of electronic switch gates of the coincidence type wherein the gate may be capable of opening or closing a signalling or control path between other elements depending upon the coincidence of at least two electrical conditions applied to the gate.

Referring now to Fig. 1, a local pulse source 10 is connected by lines 11 and 12 to frequency dividers 13 and 14, respectively. Source 10 is adapted to deliver 128 negative pulses per second to lines 1l. and 12, and is of a known type. Frequency dividers 13 and 14 respectively, consist of electronic counting chains, each stage of which is comprised of a pair of electron devices, shown in this specification, as electron discharge devices, arranged as multivibrator pairs, each stage capable of giving an output pulse for each two applied input pulses. The principle of operation of multivibrators is well known to those skilled in the art and need not be dwelt upon here. Selector key 40 comprises a 'bi-stable electronic stage and an inverter amplifierand is adapted to produce the following: (1) a positive output 30 on the onset of a received signal 22; (2) a positive output 60 upon the termination of received signal 22; (3) a positive output 38 during intervals between signals 22. Dash timing relay 23 is a modified binary counting chain and is selectively 4coupled to selector key 40, through an electronic gate 20, the selector key 40 being operable to produce an output dash 30 in response to a received dash signal 22 over conductor 44 from a radio receiver, of which only a portion of the second detector stage 69 is shown (Fig. 4c). Thus, gate 20 is adapted to be opened by the output dash 30 coinciding with received signal 22 and pulses 16 from the source 10 and divider 13 are permitted to pass through opened gate 2.0 to the input of dash timing relay 23. Dash timing relay 23 thereupon commences counting each pulse 16 and upon receipt of seven pulses 16, delivers a voltage capable of opening electronic gate 26 at a time 3.5 seconds after the onset of dashl 30 and, upon receipt of a further number of pulses 16 totalling twelve in all, closes the gate 26 at a time 6.0 seconds after Vthe .onset of dash 30'. Conductor 56 iscoupled. between selector key 40' and gate Z6.V and over which conductor a dash-.oli

pulse 60 may be applied through the opened gate 26- toA dash register 32. Dash register 32,consists of aV conventional three-stage electronic binary counter andlderives its input from selector key 40 via conductor 56 through opened gate 26.

I further provide a space timing relay 24, fed with pulses each half-second from pulse source through frequency divider 14 via electronic gate21. Space ytiming relay 24is a modified binary counting chain andV times the space intervals between received signals 22 and if kthe space between received signals equals or exceeds the predetermined time of` l.5'seconds, the spacel timer 24 delivers an output voltage which causes gate 34 to open. Gate 34 will permit erasure pulses derived from .source 10 to pass to dash register 32 and thereby effect' erasure of any dashes which were theretofore recorded' thereon providing gate 37, disposed between source 10 and vgate 34, was caused to be openedl under control of selector key 40. There is further provided a conductive connection 31 coupling the output of gate 26 to the space timing relay 24 through a re-set gate 33 andto the frequency divider 14 through a re-setgate 33A, respectively.

The operation of the device will now be described.

with the aid of Figs. 4A, 4Bk and 4C.

The receipt of a signal at the second detector 69 of 'the receiver (Fig. 4C) results in a positive pulse'22 originating at the cathode of said second detector. This pulse is applied over conductor 44 to selector key 40 which comprises, in part, apair of ip-op tubes 40a andv 40b which tubes have a common cathode connection 'and R. C. biasing network 40C. The biasing of the .tubesi is arranged so that tube 4Gb is normally conducting`inthe absence of any received signal 22. The positive voltage 22 is applied to the grid of tube 40a,.causing t'to conduct, whereupon, tube 4Gb cuts ot thereby developingV a positive pulse 30 at its anode. Pulse 30 is applied via gas discharge tube 40e to conductor 27 leading togates 20, 28 and 29 (Fig. 4A). In the meantime, pulse source 10 has been applyingnegative pulses over conductor 11 to the input stage A of frequency divider 13. As will be seen from Fig. 4A,vfrequency divider 13 is asix (6) stage counting chain utilizing. multivibrator pairs A F and is 'adapted to deliver an outputpulse for each sixty-four (64) input pulses applied from source 10. A positive pulse 16 is derived from the left-.handtube of stage F in divider 13 upon the receipt of a count of sixty-four (64) and is applied to the suppressor electrode of gate 20. If the positive pulse 30 (indicating the presence of a received signal 22) is directly applied to the control electrode of gate coincidentally with pulse 16, gate 20 will open and a negative output pulse 20a will be derived from the anode of gate 20 to be applied to the input of stage M of dash timer 23 shown in Fig. 4B.

Dash timer 23 consists of a specialized pulse counter and utilizes a plurality of electronic devices arrangedin pairs and shown connected as multivibrators. Dash timer 23 contains four (4) stages, M P, eachrstage constituting a binary counter, the output of onestagefeeding the input to the next successive stage. Dashtimer.. 23 is similar to frequency divider 13 with the. exception that there is an interlock or feed-back between stages. 0 and M, and P and N, respectively. The interlocks or feed-back paths permit the realization of a timing., device capable of initiating an output signal in responsa to a predetermined number of appliedV input pulses. The details of the voperation* of the timing' relay fareV minutely explained in my co-pe'nding application bearing Serialll develops a positive voltage at its cathode, which voltage is applied to re-set bus number lA of the dash timer 23 and causeseach right-hand tube of stages M S thereof to conduct thereby-restoringdash timer 23 to its original condition. It should be noted that gate 29 vis condenser-coupled to conductor 27, but that gate 20 is directly coupled to conductor 27. Thus, gate 20 will be primed to conduct as long as pulse 30 persists, but gate 29 will conduct but momentarily since the pulse 30 is dierentiated over the R. C. network coupled to the control electrode ofgate 29. To return'to the operation of dash timer. 23, negative `pulse 20a will be applied each half-second to the :input of stage M as long as gate 20A remains open; the gate 20 remaining open only during receipt of signals ,22. The operation of dash timer 23 can be readily followed by referring to the chart contained in Fig. 6A. From an examination of the chart it will be seen that upon the. receipt of the seventh pulse throughfthe gate 20, the dash timer 23 will deliveria positive output pulse 25. The seventh pulse coincides with aV time duration of 3.5 seconds after the onset of .the

received pu1se 22 at receiver detector 69. It will thus edge of 'pulse 25 derived, from stage P of dash timer 23, is applied to the control electrode of gate 26-thereby conditioning it for coincidence operation by positive pulse 60 which will be received over conductor 56 fromfthe anode of tube 40d in selector key 40 upon termination of received signal 22. Since tube 40b -is normallyy conductingduring the absence of received signals 22, the voltage at the anode thereof is low and tube 40d is therefore cut olf. As a signall22 is received, tube 40b cuts oli -and .tube 40d will conduct delivering a negative pulse to conductor 56. Upon the termination of received signal 22, tube 40d will cut otf and will thereupon apply the differentiated dash-off pulse 60 to the suppressor electrode of gate 26. If, at the moment of the application of pulse 60`to gate 26, stage P of dash timer.23 will have primed gate 26 byl applying a positive voltage to the cony trol electrode thereof, gate 26 will open and pass` the pulse 60'to the input of dash register 32.

Dash register 32'is a three (3) stage binary counter.

similar to frequency divider 13 and consists of multivibrator stages QR and S. In all of theA multivibrator stages utilized in this embodiment, the right-hand-stage is assumed`to be normally conducting. Thus, the application of a negative pulse from the anode of gate 26upon the coincidence of pulses 2S and 60, causes onev pulser (corresponding to anacceptable received dash 22) to` be registeredin register 32. Upon the receipt of four'(4) pulsesfrom gate 26,v dash register 32 will deliver a positive.,output from the right-hand tube of its stage S over conductor 32a to the alarm device 63. Alarm device 63 comprises an electron discharge tube 63a, a relay 63/1 serially connected in the discharge path thereof, alarm bell 63el controlled by a contact ot' relay 63h and a manual re-set key 63d all connected in an obvious circuit. Tube 63a is normally biasedito cut-off but upon application of a positive pulse from register 32, tube 63a willvr conductand relay 63b will become energized and alarm bell 63C will sound. lt will require-manual operation of re-set 63d to open the holding circuit forrelay 63h, since the right-hand contact of relay 63b closedthe holding circuit therefor upon actuation thereof. The operation described thus lar assumes the receipt of the proper number of dashes and having the proper duration,

to wit, from 3.5 to 6 seconds and spaced less than 1.5 sec-- onds apart. In the event that dashes of improper duration `are received, or that the space between dashes of acceptable duration eXceeds 1.5 seconds, any count registered on dash register 32 will be cancelled in the following manner:

If the received dash 22 is shorter in duration than 3.5 seconds, gate 26 will not have been opened since dash timer 23 delivered no output and the pulse 60 derived from the trailing edge of the pulse 22 received from the receiver detector 69, will not have been able to pass through the closed gate 26 and consequently, no pulse will be registered on register 32. The space timing relay 24 is adapted to time the intervals between dashes. The correct interval is less than 1.5 seconds and the space timing relay exerts control over the dash register so that if the time period between acceptable dashes does not exceed 1.5 seconds, the dash register will continue to count. If the spacing between dashes exceeds 1.5 seconds, the space is too long and the dash count on the register will be erased by a pulse from the source 1t). The erasure is achieved as follows:

The opening of gate 2t causes a negative pulse to be applied via conductor 31 to the grid of inverter tube 33a (Fig. 4B). Tube 33a is biased so as to be normally conducting. The negative pulse received over conductor 31 causes inverter tube 33a to cut oit and a positive pulse is derived from the anode thereof and is applied to the control electrode of gate 33. Gate 33 which is normally cut off thereupon conducts and a positive potential is derived from the cathode thereof and is applied to conductor 31a as well as to re-set bus number 2, which resets frequency divider 14 so as to re-set same to the zero state or in condition to deliver a single output for each 64 pulses applied from source 1t).

Frequency divider 14 is a duplicate of frequency divider 13 and consists of stages G L. Output pulses 17 from the stage L is applied to the suppressor electrode of gate 21. Each time that tube 33 conducts, frequency divider 14 and space timer' 24, respectively, are re-set to their initial condition, to wit, the right-hand tube of each stage will be caused to conduct. During the time that no pulse is received over conductor 31, pulses 17 from the divider 14 initiated in the source 1t) and applied over conductor 12 to the G stage of the divider 14, will appear every half-second through gate 21 to the input of stage T of space timer 24. Stages T and U of space timer 24- are interlocked so that upon the receipt of the second pulsethe condition of stage T is reversed. The operation of space timer 24 can be readily followed by referring to the chart contained in Fig. 6B. Upon the application of the third pulse 17 (corresponding to a time 1.5 seconds after the cessation of an acceptable signal 22) to the space timer 24, stage U triggers stages V and W simultaneously. The right-hand tube of stage V thereupon cuts oi and applies a positive pulse 42 to the control electrode of gate 34 opening same. Stage W simultaneously applies a negative pulse 41 to the control electrode of gate 2l causing the gate to close. It will thus be seen that gate 34 opens 1.5 seconds following the termination of an acceptable dash 22 and remains open until a subsequently received dash 22 is accepted. Posi tive pulse 3S is derived from coupling to gas discharge tube 40f (Fig. 4C) and is applied to the control electrode of gate 37 via conductor 37a. Gas discharge tube /itlf breaks down when tube 40d becomes non-conduct ing during the time that no signal is being received from the receiver detector 69. It gate 3'7 is open (no signal 22 being received) and if gate 34 is open, inverter tube 36a will be cut off thereby producing a positive pulse which 4is applied to the input of re-set tube 36 causing it to conduct and to apply a positive potential to re-set bus number 4 in the dash register 32. The application of a positive potential to the re-set bus 4 will cause the right-hand tubes of stages Q, R and S to conduct and.

any count stored in the register will be thereby erased. Thus, no output pulse from the stage S of dash register 32 will appear on conductor 32a nor will tube 63a be triggered. ln effect therefore, an erasure of the register 32 Will occur if a space between received dashes exceeds 1.5 seconds duration. An erasure will also occur when a subsequent dash terminates while gate 26 is closed. lf a dash is acceptable because of its duration and the spacing from the previous dash is proper, the register 32 will properly record and simultaneously space timer 24 will be re-set to its initial condition by the positive voltage applied to re-set bus #3 developed by the cathode of reset tube 33. The re-setting of space timer 24 to zero closes gate 34 and again opens gate 21 readying the timer to receive a new group of divided-down pulses from source 1G. rl`his new group of pulses will time the sub-- sequent interval between received dashes. if the subsequent oasn 1s either too long or too short in duration, zg Joistol qsep no poprooal oq tou Hrm uoucutuuci su because coincidence will not occur at gate 2.5. Gate 34 will therefore be open and since gate 37 is open, an erasure of the dash register 32 will take place.

The ultimate aim of the device, to wit, the sounding of an alarm bell 63C will take place when four (4) dashes having a duration of from 3.5 to 6 seconds and separated by 1.5 second intervals have been received.

It will be noted that where a positive output is desired from any of the multivibrator stages utilized in the structure shown in Figs. 4A, 4B, 4C, a coupling is taken from the anode of the left-hand tube of the multivibrator pair and conversely, where a negative output is desired, a coupling is taken from the right-hand tube of the pair.

Pulse source 10 and frequency dividers 13 and 14 are merely illustrative ot one particular timing circuit, it being understood that any other suitable timing circuit which is productive of a sequence of equally timed pulses might also be readily substituted therefor. It may be desirable to utilize separate oscillators to drive frequency dividers 13 and 14 respectively.

By referring to Fig. 3, one may readily follow the operation of the various gates utilized in my invention.

Gaseous dischaige devices such as 40e and 40]" serve as a visible indication of the proper operation of the selector key 40, and the failure of device 40e to extinguish bctween received signals 22 would indicate that tube 40h was not conducting and therefore the selector key was not in condition to receive a subsequent signal from receiver 69.

summarizing the operation of the device, the following will be noted:

(a) A received dash of less than 3.5 seconds duration will not be recorded because gate 26 cannot open until seven pulses from the divider 13 have been counted by dash timer 23, and this count requires 3.5 seconds.

(b) A received dash of longer than 6.0 seconds duration will not be recorded because gate 26 will have been closed by the twelfth pulse received by the dash timer 23 from divider 13.

(c) A dash received more than 1.5 seconds after a previously received dash will not be recorded and will cause erasure of all previously registered dashes on the dash register 32 because space timer' will have caused gate 34 to open upon a count of three, initiated upon the termination of a received signal 22, and gate 37 will have been opened by the termination of the received signal 22 thereby permitting a pulse from source 10 to re-set the register 32.

(d) A received dash of from 3.5 to 6.0 seconds duration following a previously accepted and registered dash of a duration within the same limits, and having a spacing therefrom under 1.5 seconds, will be properly recorded, because no erasure pulse may pass through closed gate 37 when a received signal 22 is applied to selector lkey 40.

(e)" Four acceptable received signals22 will cause the alarm device '63 to operate.

While I haveedescribed above the. principles of my invention in connection with specific apparatus, it is to be clearly understood ythat thisdescription is made only by way of exampleand notas a limitation to the scope of my invention.

' What is claimed is:

1. An automatic alarm-device responsive to a. predetermined sequence of received signal dashes of predetermined length separated by spaces of` a definite length comprising signal receiving means, electronic switch means coupled to and adapted tobe controlled by said receiving means, said switch means adapted to deliver a plurality of c ontrol potentials,-dash register means for registering ydash ,signals of saidpredetermined length, first electronic timing means for measuring minimum and maximum duration of acceptable receivedda'sh signals, second electronic timing means for measuring maximum duration of acceptable spaces between receivedacceptable dashes, Va coincidence gate havingtan output coupled to said register means. and said second timing means and having inputsconnected to said'lirst` timing means and a first oneof said controlpotentials,,respectively, said first timing means coupled toa second one of said control potentials for co joint.control, registercancelling means coupled between said second `timer and said register, said last named means ,under thepjoint control of said second timer and a third one of said control potentials, whereby registration on saidregister means will be cancelled in lthe event of a space of longer duration during reception of said predetermined signal sequence.

2. In anA automatic alarm device, register means adapted to record dashes of predetermined lengthand to he reset to Vzero reading by anerasurepulse upon receipt of Ydashes of non-acceptable lengthtor spaces'therebetweenin excess of a maximum time duration, signal receiving means, electronic switch means coupled to said receiving means and adapted to be controlled thereby, said switch means adapted `to deliver a plurality of control potentials in accordance with the character of signals receive'dby said receiving means, a source of erasure pulses, a source of timing pulses, a pair,ottimingcircuits responsive'to a sequence of input timing pulses tovproduce time 'delayed output signals, means including `a first one ofsaid control potentials for initiating timing action of one of said timing circuits responsive to the reception of a signal dash by said selector circuit, means responsive to the termination of saidreceived dash for initiating operation of said second timing circuit, a'lirst. gate connected between said registering means and said switch means and responsive to an output signal "from said firsttiming circuit and said second controlpotential, said 1gate adapted to be gated openV in time delayedrelation'to the start of an output signalfrom saidiirst'timing circuit, and to be gated closed a predetermined time intervalV thereafter, a second gate connected between said second'timinglcircuitand said-registermeans Aand adapted Vto be gated open a predetermined time interval after initiation of said second timing circuit in response to the `termination of the received dash, athird gate connectedbetween said switch means, said-second gate, and said source of timing pulses, said third gate adapted-to be-gated open-under control of said thirdcontrol potential upon termination of a received dash l,andtotbe gated closed at the startvof a subsequently received dash, whereby a received ydash of less than ormore 'than minimum length .is prevented from actuating -said lregister bythe `closed state of .said first gate, while ldashes of Aacceptable length find said first gate open and effect actuation of said register, said second gate being maintained closed during-an interval corresponding to the maximum time' period Yof an acceptable space to prevent an erasure pulse from erasing said register, and thereafter opens, said third gate Vbeing maintained-open throughout all space intervalsv to permit, .incooperation with said secondz gate,'the Vapplicationof an erasure pulse to said register means in responsetov a space exceeding said maximum time interval.

3. `The device of claim l wherein both said dashtiming means and-said space timing means include counting circuits operable in response to a predetermined number of timing pulses'to actuate said associated gate respectively to a gate openstate and a gate closedv state,means for the initiation of a sequence of timing pulses,jand gate means interposed betweensaid timing pulse initiating means andi-said dash timing means and between said pulse timing means and said space timing means respectively, and means associated with said switch means and operative in response to a received pulse and to a received dash, respectively, for the initiation by a start and termination of a received dash of said corresponding dash timing means and said space timing-means respectively.

-4. In an electrical network, including means for deriving a plurality of control potentials :from received signals comprising dashes and intervening spaces, a dash timingmeans, a space timing means, a 1dash register, a source of timing pulses, a warning signal coupled to said register, and a plurality of pulse responsive gates operatively associated therewith for actuation in response to an input signal comprising dashes and spaces introduced tosaidnetwork for actuation of said dash register only in response to dashes of predetermined length `and `separated by spaces ofjpredetermined intervals, andfplurl gates including a first gate disposed between said timing pulse source and said dash timing means in a manner to be gated openby application of a first one of said control'potentials derived from the leading edge of-an introduced dash and to be gated closed by the trailing edge of said dash and to remain closed during a subsequent space interval, a second gate connected between said timing pulse source and said space timingrneans in amanner to be gated open in response to the termination of an acceptable dash and gated closed by action of said space timing means .a measured time interval after termination of an acceptable dash, a third gateyconne'cted betweensaid dash timing means and said dash :register in a manner to be gated open in response to a second one rof said control potentials derived from a dash ofV minimum length and to be gated closed at the end of a measured time interval, a fourth gate connected-between said space timing means and said dash register in amanner to be gated ,open kby said space timing means after a measured time interval following termination of an acceptable dash and to be gated closed in response' to termination of a-subsequent dash, and a fifth gate con-l nected between said timing pulse source and said lfourth gate in a manner to be gated .open by application fof a third one ofV said control potentials derived upon termination of a ldash and to remain open throughout space intervals and then to be gated closed upon removal of saidthird controltpotential throughout reception of subsequent dashes.

5. In a warning signal device, the combination including an oscillator, a first and second frequency divider input for received signals comprising dashes and spaces,

and including three output circuits, a first of which is permanently connected to said first gating device, -the second and third output circuits being selectively responsive to anfinput dash and an input space respectively,

Vsaid first `mentioned circuit being productive f a square wave output in response to the rise and fall o'f an input dash, said second output circuit being productive of a differentiated pulse in response to the fall of an input dash, and said third output circuit being productive of a square wave in response to and proportional to a space, a dash register, a third gating device having its output coupled to said register, and its inputs coupled to the output of said dash timing relay, and said second output circuit respectively and adapted to be held open by a timed signal output from said dash timing relay in respect to a time base locked to the leading edge of a signal dash to permit an output pulse from said second output circuit to pass to said dash register for actuation thereof when in coincidence with the timed signal output from said dash timer, means connecting the input of said dash register to said space timing relay and to said second frequency divider for resetting thereof and opening of said second gate by a pulse initiated by termination of a dash passed through said third gating device, means connecting said space timer to said second gating eidvce to effect closing by a space timer output signal initiated by a sequence of timing pulses from said second frequency divider, fourth and fth gates series connected between said oscillator and said dash register, means connecting said fourth gate to the third output circuit of said switch means for actuation thereof to an open .state by a space initiated output signal, and means con- 6. The device of claim 5, wherein reset circuits are series connected respectively between said first output circuit and said first frequency divider and said dash timing relay, between said dash register input and said space timing relay and said second frequency divider, respectively, and between said fifth gating device and said dash timer.

7. The device of claim 5, including a warning device connected to the output circuit of said dash register for actuation by an output circuit of said dash register for actuation by an output pulse therefrom, said dash register being productive of a warning devicetactuating pulse in response to reception of a plurality of dashes passed thereto through said third gate, said dashes being separated by spaces Vof time intervals as to close said fifth gating device during open periods of said fourth gating device.

References Cited in the le of this patent UNITED STATES PATENTS 1,967,396 Chauveau July 24, 1934 2,235,804 Macalpine Mar. 18, 1941 2,418,521 Morton et al Apr. 8, 1947 2,514,889 McGoin July 11, 1950 2,533,765 Chauveau Dec. 12, 1950 2,761,060 Bradley et al Aug. 28, 1956 

